A continuing need exists for improvements in residential hot water systems, in order to reduce energy usage. Also, it would be advantageous if biological growth experienced in such systems were substantially reduced or eliminated. Further, it would be advantages if such improvements were available either in a “built-in” form and integrally provided with a new water heater, or in an “add-on” form, suitable for either retrofit or in combination with a new water heater.
Further, although I have previously disclosed various attempts at such improvements, by continuing to work in the field, I have discovered that further refinement of the basic concept of use of thermosiphons in water heaters would be yet further advantageous. In U.S. Pat. No. 4,777,347, issued to B. J. Mottershead on Oct. 11, 1988, and entitled Electric Water Heating Tank with Thermosiphonic Circulation for Improved Heat Recovery Rate, I disclosed the concept of the use of a liquid loop external to a water heater tank as being helpful in improving the heat recovery rate in hot water heaters. In U.S. Pat. No. 6,370,328 B1, issued to B. J. Mottershead on Apr. 9, 2002, and entitled Water Heating Tank with Thermosiphonic Circulation for Improved Heat Recovery Rate, I disclosed the concept of the use of an internal liquid loop circulation pipe in a water heater tank, coupled with a check valve between the hot water outlet and the cold water inlet, as being helpful in improving the heat recovery rate in hot water heaters. The disclosures of each of those prior United States patents are incorporated herein in their entirety by this reference.
A common problem encountered with my prior art devices when use was attempted in various new or retrofit construction settings is that the concepts required apparatus not normally provided either as an integral component of a hot water heater, or as a readily available and easily installable add-on component to a hot water tank installation. Thus, such prior art hot water tank thermosiphonic circulation devices inevitably present difficulty to plumbers or to the general public with respect to implementing an improved, more efficient hot water system.
Thus, there remains a continuing unmet need for (a) a hot water tank design which includes, factory build in a tank, a reliable thermosiphon configuration, and alternately, (b) a thermosiphon apparatus design which is easily can be easily retrofitted to existing hot water heaters, or added at time of construction to new hot water tank installations.